Incorrect markdown link in sharding.ipynb

The `colabs/sharding.ipynb` notebook contains a link to the example file `sharding.py`.
Currently, the link is rendered as plain text, which makes it non-clickable.

It should be updated to use proper Markdown link syntax so that users can easily navigate to the example. This will improve readability and overall user experience.

I’d like to work on this issue. Could you please assign it to me?

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**Screenshot:**